Seoul, South Korea (CNN) -- Just hours after the United States warned that North Korea would achieve nothing with threats or provocations, Pyongyang moved a long-range rocket it plans to test fire to a launch pad Monday, a South Korean defense ministry official said.

The news broke at the start of a two-day nuclear summit in Seoul that is bringing together leaders from the United States, Russia, China and dozens of other nations to discuss how to deal with nuclear terrorism and how to secure the world's nuclear material.

But North Korea's announcement that it plans to carry out a rocket-powered satellite launch in mid-April is overshadowing a message of international cooperation for the summit.